Big Bush, sometimes known as Big Wood in the early days of European settlement, is a locality between Kikiwa and Tophouse.
In February 1846 Charles Heaphy with his trusty guide Kehu, William Fox and Thomas Brunner set out to find suitable grazing land beyond Rotoiti.
They travelled with packhorses to carry provisions as far as Big Wood and then as Heaphy describes in his diary, continued on foot with 75 pound packs on their backs, looking rather like "huge peripatetic mushrooms".
I suspect your journey through here will be much quicker and much easier, whether you choose to travel by bicycle or car, or you choose to walk. Life is so different now.
Ref: "Difficult Country, An Informal History of Murchison" by Margaret C Brown.